class Student(object):
    def __init__(self,score):
        self._score = score



    @property
    def score(self):
        return self._score

    @score.setter
    def score(self,score):
        if not isinstance(score, int):
            raise ValueError('score must be an integer!')
        if score < 0 or score > 100:
            raise ValueError('score must between 0 ~ 100!')
        self._score = score

    def __str__(self):
        return 'Student object (score: %s) ' % self._score

s = Student(70)
print(s.score)
s.score = 60
print(s.score)

print(s)